cnuland / llm-d-sc-cost-v2

llm-d-sc-cost-v2

cost classifier for llm-d semantic classification . Labels: MINIMAL , LOW , MODERATE , HIGH .

Architecture: sequence-classification head (requires a runtime that reads logits) , base answerdotai/ModernBERT-base .

Accuracy

Read the real-traffic row first.

Hand-authored minus real traffic: +0.119. Hand-authored held-out prompts are written in the same clean register as the anchors; real users send truncated pastes, fragments and roleplay preambles. The real-traffic row is the one that predicts production behaviour.

The eval has a measured ceiling

Gold labels were audited by blind paired adjudication in two strata — the rows this model got wrong, and a sample of the rows it got right — with the judge shown two candidate labels in random order and no indication of provenance. Roughly 4.9% of the gold labels are themselves wrong , so a PERFECT classifier scored against this eval would reach about 0.95, not 1.0 .

Read the real-traffic accuracy against that ceiling, not against 100%. Auditing only a model's mistakes would move the number up artificially; sampling the correct rows too is what makes the estimate honest, and it revealed that on ~3.3% of "correct" rows the model agreed with a bad label — meaning measured accuracy is very slightly overstated.

How the eval was built

Real-traffic rows come from WildChat-1M (ungated real assistant traffic). Each prompt was labelled independently by three models ( claude-opus-5 , claude-sonnet-5 , claude-fable-5-1 ) from the task rubric alone -- no labeller ever saw a proposed label , so agreement is evidence rather than assent. Only unanimous rows are scored.

Those three agree unanimously on roughly 70-74% of real prompts. The remaining prompts are published as a contested split rather than discarded: they measure how much real traffic this taxonomy does not resolve, which no single accuracy figure can express.

Training data

11403 rows from cost-v2:5970+cost-real:6700 , mixing jury-labelled real traffic (register and class prior) with rubric-grounded synthetic data (coverage of tiers that are rare in real traffic). Training prior: {'MINIMAL': 2524, 'LOW': 3768, 'MODERATE': 3647, 'HIGH': 1464} . Held-out eval prompts are excluded by content hash.

Latency

CPU single-request: p50 16.58 ms, p99 18.38 ms (Apple M-series, single thread). llm-d-sc serves the classifier on CPU, so model size trades directly against per-replica throughput.

Limitations

• WildChat is consumer traffic. For sensitivity it is ~93% PUBLIC and cannot measure the tiers that gate egress; the enterprise row above covers those.
• Labels come from LLM jurors, not human annotators. The rubric was validated by reproducing the project's hand-authored gold labels (complexity 0.9875, cost 1.000, sensitivity 1.000) before use.
• Not independently reproduced.